Assessment of Ferocactus gatesii Populations in Bahía de los Ángeles using Manual Collection and UAVs
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Description
Bahia de los Angeles is an archipelago consisting of 16 islands with diverse cactus populations (West 2002). Restricted to a subset of these small islands is an endemic cactus, the Bahía de los Ángeles biznaga (Ferocactus gatesii). Despite its rarity, and loss of individuals due to illegal harvesting, there have been no quantitative surveys of this population, and little is known about their recruitment or ecology (West 2002). The goal of this study is to assess the F. gatesii populations in Bahia de los Angeles using both terrestrial and Unmanned Aerial Vehicle (UAV) methodologies, to assess the accuracy and effectiveness of UAV census for this species. From a total of 16 islands in Bahía de los Ángeles, a subset of three islands were selected for this study. Dronedeploy was used to capture images, stitch them together, and form a high-resolution image of the island. These images were used to identify individual F. gatesii, and each was measured ('trunk' diameter) and assessed for reproductive status (flowers). The same parameters were collected on the ground. Surveyors walked the entirety of the islands and identified individual cactus. All parameters collected through field work were compared to those collected using UAVs. Preliminary analysis shows the UAV can correctly identify 100% of F. gatesii greater than 18 cm in diameter, while also identifying reproductive status. This suggests that, for monitoring adult populations of this threatened endemic, UAV surveys provide a rapid and effective method, but that there may be limitations in identifying newly-recruited individuals.
Assessment of Ferocactus gatesii Populations in Bahía de los Ángeles using Manual Collection and UAVs
Bahia de los Angeles is an archipelago consisting of 16 islands with diverse cactus populations (West 2002). Restricted to a subset of these small islands is an endemic cactus, the Bahía de los Ángeles biznaga (Ferocactus gatesii). Despite its rarity, and loss of individuals due to illegal harvesting, there have been no quantitative surveys of this population, and little is known about their recruitment or ecology (West 2002). The goal of this study is to assess the F. gatesii populations in Bahia de los Angeles using both terrestrial and Unmanned Aerial Vehicle (UAV) methodologies, to assess the accuracy and effectiveness of UAV census for this species. From a total of 16 islands in Bahía de los Ángeles, a subset of three islands were selected for this study. Dronedeploy was used to capture images, stitch them together, and form a high-resolution image of the island. These images were used to identify individual F. gatesii, and each was measured ('trunk' diameter) and assessed for reproductive status (flowers). The same parameters were collected on the ground. Surveyors walked the entirety of the islands and identified individual cactus. All parameters collected through field work were compared to those collected using UAVs. Preliminary analysis shows the UAV can correctly identify 100% of F. gatesii greater than 18 cm in diameter, while also identifying reproductive status. This suggests that, for monitoring adult populations of this threatened endemic, UAV surveys provide a rapid and effective method, but that there may be limitations in identifying newly-recruited individuals.